Hey hope you haven't given up yet . I have been fighting with the same problem . today my problem got worse, misfiring, black smoke hard to start ect. the second time I took apart the carb I noticed the piston power ( thats the brass tube with the brass barrel with the big spring in it ) wasn't traveling very much in its hole. hope you aren't having trouble following my high tec speak. anyway I rolled up a piece of 220 sandpaper like a funny jamaican cigaret and polished the port this fits in until it worked smoothly , I was surprised how bad just a little crud was affecting this part. I put it all together and now it runs like it was touched by god ! hope this helps , at least it won't cost you anything.
